1. Field of the Invention
This application is a continuation-in-part of U.S. application Ser. No. 06/526,152, filed Aug. 24, 1983. The present invention relates to an armature for an electrical device and to a method of connecting an armature winding to an armature termination, the armature termination being connectable to an external circuit.
In the manufacture of an armature for an electrical device it is necessary to provide an electrical connection between the armature and the commutator of slip ring which is used for effecting electrical contact between the armature winding and an external circuit.
2. Description of the Prior Art
A number of known methods for effecting such connections are in popular use. Where the winding is formed of low temperature wire it is usual to employ a soft solder and flux method or alternatively a cold crimp onto wire that has been stripped of insulation is used in order to effect a connection. When dealing with high temperature wires it is necessary to apply heat, and also possibly to apply flux so as to remove the coating of insulation from the end of the magnetic wire. Typical methods are hot forging, electric welding and gas welding. Occasionally such welding is undertaken in combination with sophisticated inert gas shrouds in order to minimize oxidation.
However, there are a number of inherent problems and undesirable side effects associated with all of the foregoing methods.
Heat causes embrittlement of the copper wire which is used for most armature windings and encourage rapid oxidation. The use of heat also demands a strong structure to support the commutator in order to minimize plastic distortion during soldering, forging or welding. This requirement usually demands the use of high temperature compression grade molding resins. A further common problem is caused by the accidental stripping of insulation during winding of the armature which is ofter automated. As the wire passes over the metal of the commutator damage can be caused to the wire insulation and such damage will ofter be manifest as a short circuited winding. Additionally, there is always a danger of slack in the winding wire causing fretting under the acceleration due to centrifugal and inertial forces.
These disadvantages place considerable limitations on the design and manufacture of commutators especially when such factors are closely cost controlled.